1. Field of the Invention
This invention relates to an examination system to be used for examining semiconductor wafers.
2. Related Background Art
A semiconductor device is prepared by forming an exquisitely fine device pattern on a semiconductor wafer. When forming a device pattern, particles of dirt can adhere to the surface of the semiconductor wafer and/or the wafer can be damaged to make the wafer defective. A semiconductor device formed on such a defective wafer is a defective device that reduces the overall yield of manufacturing semiconductor devices.
Therefore, to hold the yield of the manufacturing line to a high level, defects caused by dirt and damages have to be detected in earlier stages and the causes of the defects should be identified so that effective counter measures may be taken for the manufacturing facility and the manufacturing process.
It is a common practice that, when a defect is detected, it is examined by means of an examination device to identify the type of the defect and also the facility and the process that produced the defect. The examination device for examining the type of the defect is typically an optical microscope that produces an magnified image of the defect to make it possible to identify the type of the defect.
In order to improve the manufacturing facility and the manufacturing process on the basis of the detected defects, it is desirable to examine semiconductor wafers as many as possible for defects and pin-spot the right causes of the detected defects. However, as device rules are downsized for semiconductor wafers, there arise a variety of defects to make it difficult to visually identify defects in a short period of time. To cope with this problem, there have been proposed automatic defect classification systems adapted to pick up an image of the surface of a semiconductor wafer and automatically determine the type of the defects found on the semiconductor wafer on the basis of the picked up image.
However, known automatic defect classification systems need improvements for more accurately identifying the type of each defect found on a semiconductor wafer.